The orifice plate of the printhead of an ink-jet printer, particularly a thermal ink-jet printer, tends to pick up contaminants, such as paper dust, and the like, during the printing process. Such contaminants adhere to the orifice plate either because of the presence of ink on the printhead, or because of electrostatic charges. In addition, excess ink can accumulate around the printhead, if all the ink is not pumped out of the printhead. The accumulation of either ink or other contaminants can impair the quality of the output by interfering with the proper application of ink to the printing medium. For these reasons, it is desirable to clear the printhead orifice plate of such contaminants on a routine basis to prevent the build-up thereof.
Wipers are known in the prior art for removal of contaminants from the orifice plate of the printhead. One type of stationary wiper found on existing machines is described in U.S. patent application Ser. No. 149,454, now U.S. Pat. No. 4,872,026 issued Oct. 3, 1989 filed on Jan. 28, 1988 and assigned to the assignee of the present application. This wiper typically comprises a resilient material, such as nitrile rubber, and is disposed in the service station area of the printer. The service station provides a region at one end of the bi-directional movement of the print head carriage which holds the printhead carriage in locked alignment. Typically, the printhead is dragged across a stationary wiper blade as the printhead carriage moves into the service station area. The wiper itself is cleaned by downwardly facing edges on a lower side of the printhead which are dragged across the wiper subsequent to the printhead.
Another type of prior art printhead wiper includes a flat ring having a plurality of upstanding, resilient, widely spaced blades disposed on an outer surface thereof. The blades are disposed generally orthogonally of the ring. The ring typically is stretched between two shafts, and this ring is selectively driven by a motor or other like device which is coupled to the pulleys. No means for automatically cleaning the blades is provided. An example of this wiper is described in U.S. Pat. No. 4,577,203.
Prior art wipers, including those described hereinabove, suffer from a number of drawbacks. In the first place, inadequate means are provided to remove contaminants from the wiper itself after it has cleaned the printhead orifice plate. Contaminants are only periodically removed and the apparatus used for removal does not entirely clean the wiper after each use. As a result, subsequent passes of the wiper over the printhead tend to recontaminate the printhead. Secondly, inadequate cleaning is provided because typically only one upstanding wiper blade wipes the printhead during each pass of the printhead over the wiper, thus removing only some of the contaminants during any one pass. A number of passes is required to remove a sufficient amount of such contaminants.
It is therefore an object of the present invention to provide a wiper for an ink-jet printer which removes substantially all of the dust, ink and other contaminants from the printhead orifice plate during each pass of the printhead over the wiper.
It is a further object of the present invention to provide a wiper for an ink-jet printer which includes means for automatically cleaning the wiper as it wipes the orifice plate of the printhead.
It is another object of the present invention to provide a simplified wiper mechanism which is effective in removing paper dust, ink and other contaminants from the printhead orifice plate of an ink-jet printer.
It is another further object of the present invention to provide a simplified wiper for ink-jet printers which is actuated only when the printhead passes thereover.